Omeprazole, chemically 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)methyl]sulfinyl]-1H-benzimidazole and its therapeutic uses were disclosed in European Patent No. 5129. Omeprazole is a well-known gastric acid secretion inhibitor, and is useful as an anti ulcer agent. Omeprazole has a stereogenic center at sulfur and therefore exist as two optical isomers such as R-omeprazole and S-omeprazole (esomeprazole).
The alkaline salts of (S)-enantiomer of omeprazole (esomeprazole), the pharmaceutical preparations of these salts and the method of treatment of gastric acid-related diseases using them were disclosed in U.S. Pat. No. 4,738,974, U.S. Pat. No. 5,877,192 and U.S. Pat. No. 5,714,504. The U.S. Pat. No. 4,738,974, U.S. Pat. No. 5,877,192 and U.S. Pat. No. 5,714,504 are incorporated herein by reference.
These compounds and structurally related compounds have a stereogenic center at sulfur and therefore exist as two optical isomers. The resolution processes of racemates of these compounds were, for example, disclosed in DE 4035455 and WO 94/27988. According to these processes chiral ether such as fenchyloxymethyl or chiral acyloxy methyl group such as mandeloyl- is introduced into the 1-position of benzimidazole ring of racemic sulfoxide compound to obtain a diastereomeric mixture, diastereomers are then separated and desired isomer is liberated from a separated diastereomer. The process requires either the preparation of fenchyloxymethyl chloride and then reaction with the racemic compound; or introduction of chloromethyl group on 1-position of benzimidazole ring, followed by reaction with the chiral auxiliary. We found that these intermediates are difficult to prepare and involve in many steps.
PCT Publication No. WO 94/27988 disclosed certain salts (sodium, magnesium, lithium, potassium, calcium and alkyl ammonium salts) of single enantiomers of omeprazole and processes for their preparation thereof. These compounds have improved pharmacokinetic and metabolic properties which will give an improved therapeutic profile such as a lower degree of interindividual variation.
PCT Publication No. WO 96/02535 disclosed a process for the preparation of the single enantiomers of omeprazole and structurally related compounds as well as salts thereof.
PCT Publication No. WO 97/02261 disclosed a process for the optical purification of certain enantiomerically enriched benzimidazole derivatives by using a crystallization method.
PCT Publication Nos. WO 2008/004245, WO 2006/094904, WO 2007/013743, CN 1087739 and CN 1223262 disclosed-processes for preparation of an optically pure or optically enriched enantiomer of a sulphoxide compound using R- or S-1,1′-bi-2-naphthol (R- or S-BINOL).
The resolution of sulfoxide compounds including racemic omeprazole were described in PCT Publication No. WO 2004/002982. The method requires expensive reagents like titanium compounds, two chiral reagents namely diethyl-D-tartarate and L-Mandelic acid.
Enantioselective synthesis was described for example in Euro. J. Biochem. 166 (1987) 453 and U.S. Pat. No. 5,948,789. Disadvantages of these methods are that strict control of conditions is to be maintained and strict control of quantities of oxidizing agents is required for avoiding oxidation of desired sulfoxide to sulfone impurity. Moreover, these methods require expensive reagents like titanium isoproxide and diethyl-D-tartarate.
U.S. Pat. No. 7,176,319 B2 disclosed a resolution of racemic sulfoxide compounds using chiral camphoursulfonyl chloride.
U.S. Pat. No. 5,948,789 and U.S. Pat. No. 7,365,206 B2 disclosed stereoselective oxidation methods for the preparation of chiral substituted 2-(2-pyridinylmethylsulfinyl)-1H-benzimidazoles.
PCT Publication No. WO 2007/074099 disclosed process for the preparation of optically pure benzimidazole derivatives by inclusion complex with (S)-1,1,2-triphenyl-1,2-ethanediol.
Resolution of omeprazole with chiral 1,1′-binaphtyl-2-2′-diyl hydrogen (BNPPA) was disclosed in co-pending Application No. PCT/IN2009/000567.
PCT Publication No. WO 2008/092939 disclosed a process for the preparation of substantially optically pure omeprazole with the formation of a complex by using chiral amine or chiral quaternary ammonium salt. Magnesium salt of esomeprazole trihydrate was disclosed in PCT Publication No. WO 98/54171. Barium salt of esomeprazole was disclosed in PCT Publication No. WO 2004/099181.
U.S. Patent Application No. 2005/0182099 disclosed tert-butylammonium salts of omeprazole and esomeprazole.
U.S. Patent Application No. 2007/0004778 disclosed adamantan ammonium salt of omeprazole and esomeprazole. Esomeprazole arginine salt was disclosed in PCT Publication No. WO 2007/071444.
PCT Publication No. WO 2009/047775 disclosed a process for the preparation of high assayed esomeprazole magnesium dihydrate substantially free of its trihydrate form from esomeprazole or esomeprazole sodium and also disclosed crystalline form 1, form 2 and amorphous form of esomeprazole calcium salt.
One object of the present invention is to provide a novel process for the resolution of omeprazole.
Another object of the present invention is to provide a novel compound of enantiomers of omeprazole cyclic amine salt and a process for preparing it.
Another object of the present invention is to provide a solid of (R)- or (S)-omeprazole cyclic amine salt and a process for preparing it.
Another object of the present invention is to provide a process for the preparation of esomeprazole magnesium dihydrate substantially free of its trihydrate form.
Still another object of the present invention is to provide a process for the preparation of recovery of chiral BINOL.